Metal forming

ABSTRACT

A sheet of material is placed over a die cavity. A ram made of malleable material, such as lead, forces the sheet into the cavity. The force of the ram, progressing inwardly from the edges of the sheet toward the center of the cavity, moves the sheet downward and inward into the cavity, without appreciable change in the thickness of the material at any point. The sheet may thus be worked in cold condition, either in one or a succession of steps, without requiring heat treatment.

United States Patent [1 1 Greer et a1. Nov. 27, 1973 METAL FORMING1,424,406 8/1922 Hauptmeyer 72/60 2,280,359 4/1942 Trudell 72/60 [75]Inventors. Walter Greer, Lynwood, Richard 2,292,462 8/1942 Milford 72/6OSeal Beach both of 2,927,549 3/1960 Derbyshire 72/54 Calif.

[73] Assignee: Greer Products, lnc., Los Angeles, Primary ExaminerverlinPendegrass C lif, Att0rney-John N. Hazelwood, Albert J. Miller, Robt H.F d R b t S. S k 22 Filed: Dec. 1, 1967 er raw er wec er Appl. No.:692,627

Related US. Application Data [5 7 ABSTRACT A sheet of material is placedover a die cavity. A ram made of malleable material, such as lead,forces the sheet into the cavity. The force of the ram, progressinginwardly from the edges of the sheet toward the center of the cavity,moves the sheet downward and inward into the cavity, without appreciablechange in the thickness of the material at any point. The sheet may thusbe worked in cold condition, either in one or a succession of steps,without requiring heat treatment.

23 Claims, 14 Drawing Figures PATENTEDHGVZ? I873 SHEET 1. BF 3 M447521), 612552 12/044120 C. SCHL/CHT INVENTOES METAL FORMING RELATEDAPPLICATIONS This is a continuation of Ser. No. 51 1,484, filed Dec. 3,1965, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to deep drawing ofsheet metal into concave-convex forms, and more specifically to metalforming by a flowable mass forced into a rigid die.

Deep draw of sheet metal is a precise science modified somewhat by art.The deeper draws, and complex forms, require several steps, and oftenrequire annealwithout the requirement of destructive anneal betweenseparate forming stages.

Another object of this invention is to form a sheet of metal into aconvex fonn by wiping the metal onto a surface under an avalanche ofextruded substances of great pressure advancing along the die surface.

It is another object of this invention to provide both a novel diesystem and a method for forming of metal.

It is a further object of this invention to provide apparatus forextrusion of a mass into a die, and to trap a workpiece between saidmass and die, whereby the workpiece is caused to flow into a finishedform, in contradistinction to drawing and working of the workpiece.

A still further object of this invention is to provide a formedworkpiece substantially unaltered in gauge from its original gauge.

SUMMARY OF THE INVENTION The apparatus and process of this invention isnot a substitute for all deep-die or progressive-stage draw production.It is intended only as a means for producing deep-draw formation in oneor two operations and without work hardening in those metals which defyformation by any other process, or which otherwise require compromisesof design and repeated annealing between steps of drawing, in order toaccomplish any usable results.

In short, the apparatus and process of this invention is for the moredifficult type of forming situations.

No specific type of metal will be named as the type of workpiece uponwhich the discussed process and apparatus will operate. It will serve onany type of metal, including those that could be drawn by conventionalmethods. Furthermore, the metals which were difficult to work at thetime this invention was conceived, may be some of the easier metals towork in comparison with further metallurgical developments in the yearswhich follow this invention. Hence, it is only set forth thatthisinvention provides a means for working metal, which means is totallynovel in concept and execution from conventional deep-draw methods knownat the time of this invention, and also differs in construction,operation and result from those efforts which have heretofore attemptedto make use of a deformable lead ram to imitate conventional drawmethod.

The forming methods of this invention are radically different fromstandard procedures and there is no basis of logical comparison. Inbroad generality, this invention takes advantage of the forces involvedon the interior of an extrusion die. Extrusion is'done by forcing thematerial through a die. This invention used a closed-end die. Theextrusion begins and the material and the workpiece fill the closed die.

There is no stretching of metal by the practice of this invention, andthe uniformity with which the formed pieces retain the gauge of theoriginal workpiece defies logical prediction. Exceedingly tough titaniummetals, for example, have been formed from paper-thin sheets, and insheetssufficiently thick to be employed in military combat hats, and inboth instances, a gauge thickness of the original material is maintainedalmost without discernible change. Printing on the original metalremains substantially undistorted and readable even in the deepestportion of the finished workpiece.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an illustration of the dieand malleable ram relationship at the beginning of operation, with aworkpiece positioned above the workpiece position on the forming die;

FIG. 2 is an illustration of the die closed and the malleable ram fully'extruded into the die;

FIG. 3 is a closed die position of a second-stage oper ation at thebeginning of the malleable ram deformation step;

FIG. 4 illustrates a manner of reforming the malleable ram for reuse;

FIG. 5 illustrates the completion of the reforming step;

FIG. 6 is a vertical section of a workpiece as formed by the apparatusand process of this invention;

FIG. 7 is an open position of ram and die in an alternate malleable ramconstruction;

FIG. 8 illustrates the terminal formation condition of the malleable ramin this alternate construction;

FIG. 9 is another alternate construction for specific types of workpiecestock;

FIG. 10 is an alternate die construction;

FIG. 11 shows a form of the apparatus modified slightly over that shownin FIG. 9;

FIG. 12 illustrates a still further modification;

FIG. 13 illustrates yet another modification; and

FIG. 14 is a perspective view of another form of a more complexcontoured form, also having curvature in orthogonal planes, which may beformed by the method of the present invention simply by shaping therigid cavity appropriately.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the FIG. 1 of the drawing,the'die 10 is formed with a die cavity 12 shaped to provide a finishedconcave workpiece, suitable to serve as the basic element of a combathelmet. In some instances, a two-stage forrnation is desirable, not fromthe standpoint of workpiece requirement, but because of powerrequirement economies. Hence, a first-stage cavity may be made with apartial cavity, or the cavity 12 may be foreshortened by the use of atemporary and removable bottom filler.

In FIGS. 1 and 2, a filler plug 14 resides in temporary manner in thebottom of the die. The plug 14 is merely seated in place and isremovable.

The die cavity 12 has a bottom area below a dotted line 16, whichconstitutes the actual finished shape to which a workpiece is toconform, and above the line 16 the die is configured as an entrance rimsection 18. This rim section slopes outwardly and upwardly and is animportant functional structure which carries forth a part of the processnovel to the present invention.

It will be noted that the rim section 18 flares outwardly to define themouth or periphery of the cavity 12. Continuously circumjacent thecavity 12 is a raised rim 13, the inner periphery of which is defined bythe outwardly flaring rim section 18, and the outer periphery of whichis defined by a downward shoulder 15.

A pressure ring 20 is seatable on the face of the die 10, and ispreferably provided with interlocking surfaces which guide the ring toits proper relationship with respect to the cavity 12, and holds itthere against the lateral forces which are developed in the process. Thering serves the purpose of a removable guide through which a ram isdirected toward the cavity 12.

Within the retainer pressure ring 20 is a composite malleable ram 22.Ram 22 is composed of a steel core 24 positioned along the axis of thering 20, with an annular lead collar 26 closely fitted to the surface ofthe core and confined within ring 20. Above the collar 26 is a ram 28which can supply a large tonnage pressure. A pressure means, which isindicated by the arrows 30 in FIG. 1, holds the pressure ring 20 snugagainst the die 10, but not with any necessarily great force as isneeded upon the ram 28.

A workpiece 31, which is illustrated as being substantially circular inform to produce a bowl-shaped finished workpiece, is placed over theentrance opening of the rim 18. This is only an example form, and theinvention is not limited to a circular workpiece. The FIG. 1 does notreveal the circular nature of the workpiece, but it can be seen that thediameter of the workpiece coincides almost precisely with the diameterof the remote edge of the entrance rim 18. The face of the die has aslight step downwardly beginning at the edge of the entrance rim 18. Thepressure ring 20 fits precisely with the ledge which results.

The workpiece 31 is illustrated as a circular sheet of metal centeredover the mouth of the cavity 12. The outer edges of the sheet 31substantially coincide with the mouth or periphery of the cavity 12.

Furthermore, the diameter of the lead collar 26 is substantiallyidentical to the diameter of the workpiece 31 and the entrance rim 18.Hence, the workpiece 31 is trapped and held precisely on the entrancerim of the die by the yieldable lead. It is important to note that thereis absolutely no clamping of the workpiece between retaining surfaces ofany nature which will hold the workpiece in position against movement.The workpiece is caused to move bodily under the concept of thisinvention.

As the process of formation begins, the pressure ram 28 and the means 30move the apparatus to a closed condition wherein the workpiece 31 isheld snugly in place, but not deformed. Thereafter the pressure is in.-creased on the ram 28. Such increase in pressure ..will bring theperipheral edge of the lead collar 26 tight into contact with the edgeof the entrance rim 18 at the point indicated by the reference character32 in FIG. 2. The pressure which is applied on thecollar 26 will betranslated into contact pressure at the point 32, because this point ofcontact is an unyielding resistance.

Hence, as the pressure continues to build up, the lead of the collar 26begins to extrude into the cavity. This extrusion, when carried out inthe confinement illustrated, is an extrusion along the edge of theentrance rim at this stage of the formation, because the pressure takesplace on the peripheral portion of the lead. There is a rolling actionalong the wall of the entrance rim 18, but the center portion of thecollar simply moves downwardly. The lead advances in an avalanche androlls or wipes the workpiece against the die side wall.

It will be noted that at all times the pressure of the lead collar 26 isconfined within the mouth or periphery of the cavity 12, i.e., within animaginary cylinder centered on the center 33 of the cavity 12, whosewall or surface passes through the circular periphery or mouth of thecavity 12, as shown by the phantom lines 35 representing the wall orsurface of this imaginary cylinder.

In demonstration of this stage of the process, if the ram 28 isreversed, and the workpiece taken from the mold at this incompletestage, it is found that the peripheral edge of the workpiece has beenturned into contact with the walls of the cavity 12, and the entirecenter portion of the workpiece has remained substantially Hat, and theentire workpiece has moved downwardly into the die. Hence, a shallowdish formation results wherein the edges are shaped to conform to thedie, but are shaped to that portion of the die where the unformedworkpiece bridges, somewhat removed from the top of the entrance rim 18.Hence, the workpiece is not stretched, but the sides simply take on ashallow rim formation to the dimension of the die across a portion ofthe entrance rim a distance removed from the top of the entrance rim.

Accordingly, as the normal formation process continues after the die isoriginally closed, the workpiece turns and follows the side of the diedownwardly under the formation of the extruding avalanche of lead, untilfinally the workpiece comes to rest in the position shown in FIG. 2. Atthis position, once again, the workpiece is found to simply have anunformed bottom with turned edges, all of which have the same gaugethickness at which the original workpiece 31 was provided, and nowrinkles or other deformation defects in the workpiece can be found. Themetal of the lead collar is bright where it has had the workpiece movedout from under the forming lead as it moves downwardly. This bright areahas been moved over to conform to the shape of the die, but it is brightand polished by reason of the workpiece pulling out as it movesdownwardly to the position of FIG. 2.

The explanation of the construction and operation thus far has been withreference to a lead collar 26. It has been found that this invention isoperable with many types of malleable materials which will extrude intothe die under pressure, as described. In fact, it is necessary to useother materials for some types of workpieces. Aluminum and aluminumalloys are examples of malleable rims which are used. In some rareinstances, metals which normally are considered to be hard metals, andnot malleable and extrudable, are employed at elevated temperatures,being inserted into thepressure ring after external heating or by theuse of internally contained heating elements. Not always are suchcomplex heated malleable rams necessarily recoverable for reuse.

Whenever the malleable collar26 is placed under high pressure by the ram28, the collar material begins to flow. A body of fluid, unrestrained,acting upon the workpiece 31 would flow away from the pressure area andexert an unrestrained force upon the workpiece beyond the ability of theworkpiece to withstand. In such cases, stretching and ballooning wouldtake place and would destroy the workpiece. A malleable collar resistsfree flow to the undesired location, but under enough pressure will flowbeyond desired limits.

According to this invention, in those workpiece situations whereballooning by undesired flow would normally take place, the fluid actionof the composite malleable ram is confined to the peripheral area of thedie by the use of core.24. The core 24 is employed, not to apply a drawpressure to the central area of the workpiece, but rather just theopposite. It is used to maintain a contact with the central areasufficient to exclude the malleable material of the collar 26 from thatarea.-

Thus, it is caused to simply fill the space in the center of the coreand ride along with the receding flat surface of the workpiece.

The core 24 of. FIG. 1 is provided with a flared end 34, upon which thefluid nature of the collar 26 under pressure may act to apply a forwardforce of limited amount. This degree of flaring, as illustrated, will begenerally sufficient to cause the end of the core 24 to keep in contactwith the workpiece 31.

In order to insure the maintenance of a film contact between the coreand the workpiece, a pressuresensitive contact switch 36 is used forsome operations; the switch is designed forreaction to a predeterminedamount of pressure, as may be desired as a maximum contact pressure.Then, the core is separately driven by a power device which will forcethe core toward the workpiece independently of the force of ram 28 orthe pressure provided by the means 30. Thus, when there is a firmcontact between the workpiece and the end of the core, thepressure-sensitive contact 36 terminates the applied pressure. Hence, asthe workpiece moves away from the surface of the core, the core will beactivated to follow. No appreciable force is applied by the core 24, noris the malleable material permitted to enter the central area and causeballooning. Any small amount which can underflow the end of the corewill have negligible ballooning effect.

Referring to FIG. 2, the first stage of forming, according to thisinvention, is sometimes terminated in a foreshortened die forconservation of power requirements. The contact with the top of theremovable filler plug 14 produces a dish-shaped piece with only theextreme sides turned into an approximation of the form ultimatelydesired. It is entirely conceivable that the filler plug be eliminated,and in some situations this is actually done. However, the power neededto drive the ram 28 is excessively large in order to deform a collar oflead large enough to fill a large die cavity. For example, a cavity toform a combat helmet shell is quite large for a single operation. Thepressure must continue to act upon and extrude the lead of collar 26 inthe area from the point 32 down to the edge of the workpiece as shown inFIG. 2, although no workpiece remains in this area. Hence, such energyof deformation is wasted and requires a large press capacity. Ifaluminum, rather than lead, is used, the power requirements are evencomplete single-draw action is desirable.

In FIG. 2, the action must stop about at the position shown because ofthe presence of the non-malleable core. If this die is to be used tocompletion, a fullymalleable ram without the core must be used toreplace the composite ram. The replacement ram must have a starting formin the shape of the extruded collar in FIG. 2 to take up exactly wherethe composite ram ended. Then, the completion of the workpiece will becarried out and the lead is free to flow onto the central area where itformerly was excluded, and complete the workpiece.

As pointed out, the pressure needed to extrude such a large-sizemalleable ram is considerable. It is usually desirable to provide a diewhich is equivalent to the original die from the workpiece positiondown. Then, a smaller retainer ring is supplied which matches theentrance rim of the smaller diameter die and a fully malleable ramsubstituted for the composite ram. This ram will have a considerablysmaller diameter, and will have considerably lower power requirementsthan would be required if a full-size malleable ram were used in theoriginal die.

FIG. 3 illustrates the use of an alternate die 40 having a die cavity41, which corresponds to the needed portion of the die cavity 12 afterthe FIG. 2 state has been reached. The area of entrance rim 18 above theworkpiece in FIG. 2 is omitted, and the balance of the die 12 thencorresponds to die 41.

A malleable ram 42, which is a totally malleable lead member, may thenbe employed to continue the formation. No central core is employed inthis stage. By the application of pressure on the malleable ram 42, theformation continues along the rim area and the small amount ofballooning that can take place in the central area before the workpiecehas been formed to the contour of the die 41 is negligible. However, itis important to note that in the second-stage draw of FIG. 3, theportion of the workpiece which has been formed into the rim edge is notheld to the position shown in FIG. 3, but will follow along and slidedown further in the die as the flat portion of the workpiece is furtherformed and moved into the finished totally-formed condition. Hence, thedotted lines indicated by the reference number 43 in FIG. 3,-and asshown in FIG. 6, indicate the finished product and the amount of slidingmovement of'the sides as it moves downwardly, conforming slightly to thedifference in the cavity formation.

It is this forming of the workpiece material as it is literally pushedbefore the malleable ram that makes possible the outstanding results ofthis invention. The workpiece material is not work hardened becausethere is no inner molecular stretching and working, other than onemovement into its ultimate location. A finished workpiece coming fromthe stages as described in the FIGS. 1 through 3 comes from the die withessentially the same hardness as the original workpiece 31. This is truewhether the operation is interrupted between the stages of FIGS. 2 and3, or whether a continuous operation is carried forth from the beginningworkpiece to the finished part. Furthermore, this is true although othertypes of deep draw require numerous anneals between draw stages.

Referring to FIG. 7 of the drawings, a straight-sided core 44 is shownin the place of the flared core 24. This is an example of the type ofoperation which can go to completion in one stage. Normally, there is nopressure applied to the core 44, other than that which is natural in thefluid action of the lead as it is deformed. For this reason, thestraight core 44 tends to lag behind the workpiece and the forming leadwill underflow and form bulbs of the lead material as indicated by thereference number 46 in FIG. 8. Note in the FIG. 8 that the workpiece hasbeen formed into a finished piece 43, tight against the bottom of thedie, but the lead underflow portions 46 are not in complete contact, noris there any lead in contact with the portion of the workpiece at theexact crown of the finished piece 43.

In some operations, the straight-sided core 44 may advance either toofar or too little, and in such instances the core may be secured to thedriving ram and caused to advance with the ram. Thus, the extrudablelead collar, because it is entering a smaller area than its originalvolume, will advance ahead of the core 44 in substantially the mannerdescribed. Furthermore, a controlled advance of the core at a separaterate, under power, may be provided for other instances.

This phenomenon of workpiece formation illustrates further the fact thatthe workpiece is not drawn in the conventional manner, but is caused toturn and move into place under the extruding action of the malleablecollar. As the lead is caused to extend beyond the end of the core 44,the material of the workpiece is actually pushed ahead of the lead andfalls into place against the die, exactly as illustrated in FIG. 8. Infact, it has been found that care must be exercised not to continue thepressure on the malleable lead for too great an extent or the crownportion may be caused to actually buckle under the pressures transferredfrom further up along the side of the workpiece.

The process and apparatus of this invention deforms the ram for eachpiece drawn. One of those stages is to return the malleable ram to itsoriginal condition as shown in FIG. 1 for reuse. This is accomplished bythe ramming of the formed lead against a flat surface to push it backinto the original condition. Hence, in FIG. 4 a flat surface bridge 52is shown to have been placed over the die cavity 12, and the formed leadcollar 26, which has the outside configuration of the die cavity 12,with an indent where the workpiece finally resided, is trapped betweenthe surface of bridge 52 and the ram 28. By application of pressure andthe use of ring 20 as a mold, the lead is caused to flow back into itsoriginal condition, as shown in the final stage of reformation in theFIG. 5. As an alternate, a full plug may be placed in the die 12 andused as a flat abutment for this purpose.

Under the conditions wherein the die of FIG. 2 is employed with aseparate malleable ram to complete the formation in that die, thesecond-stage fully malleable ram will be likewise returned to itsstarting condition by placing the removable plug 14 back into the die,placing a fonned workpiece or a substitute in the die over the surfaceof the plug 14, and then driving the fullyforrned malleable ram againstthat surface to bring it back into the starting position conforming tothe upper part of the die as shown in FIG. 2.

Whenever underflow, such as shown in FIG. 8, is allowed, there will be atrapping of some of the lead under the end of the core 44 which must beremoved.

There are some workpiece sizes and metal types which are beneficiallyformed without any central core, and generally in one continuousoperation. Apparatus of this type is shown in FIG. 9, using a solid leadmember 48. Prior art structure has employed malleable lead inone-operation formation, but with conventional draw tactics wherein theedges of the workpiece are clamped. When employing the principles ofthis invention, wherein the workpiece is held only by means of themalleable material, and, therefore, allowed to slide, the formation willtake place in the manner that was described with respect to the twomalleable plugs wherein central hard cores are employed. As noted, thisalternate application is limited in the scope of workpieces and sizesbecause ballooning in the center of the lead plug will otherwise cause adestruction of the workpiece.

This construction of FIG. 9, in the process employed, does not exercisethe complete degree of control as in the embodiment employing centralcores and control of those cores, and, therefore, it is not operative tothe degree of accuracy as the core embodiments. The use of a unitarymalleable ram without a core is less costly, and may be employed foroperations wherein the degree of accuracy is not required or thematerial is not as difiicult to handle. The principles of operationremain essentially the same. The extrusion takes place from the sideedges.

The full malleable ram of FIG. 9 will begin to balloon slightly in thecenter and cause some stretching as the process takes place. Theworkpiece may actually shift laterally in the die to some degree,whereas, this would not take place in the use of the central core.Nevertheless, this FIG. 9 alternative construction is able to produce asufficient quality for many workpieces. Actually, the quality of thisalternative process is generally far greater than a similar piece madeby draw procedures. Thicker workpiece gauge will cause the slight shiftfrom ideal to a greater degree than thin workpieces, because a staticpressure must be built up before workpiece movement begins, and thegreater the static pressure, the more likelihood of one side yieldingslightly more than the other at the beginning of movement down into thedie.

In all of the die formations, the fact that the adherence of workpieceand malleable plug is so close to the die, requires a breather tube 50to bleed the air which is trapped in the die. In the event such air tubeis not provided, the air will be sufficiently great in resistance andvolume that the workpiece will be badly distorted.

An alternate construction as shown in FIG. 10 has been found useful formany applications. In this apparatus, a table 54 is provided in the dieand serves somewhat the same purpose as the flared core 24, but inreverse location. The table 54 is supported by a receding fluid pistonram 56, which has a pressure-sensitive contact 58 acting in the mannerof control or contact 36. Hence, as the lead forms along the edges ofthe die, the central area is supported against ballooning, but the tablewill recede from the workpiece as the pressure acts on the contact 58.

In FIG. 11 is illustrated a variant of FIG. 9, which makes possible theformation of even very hard-towork sheets with a high degree of accuracyand with no significant ballooning, stretching, folding or otherundesired deformations. In this embodiment, the malleable lead ram 48 isprovided with a central depression or concavity 60. This concavity makespossible the elimination of the center core 24, while still preventingballooning of the central portion of the workpiece 31. This is becausethe center portion of the sheet 31 is not contacted by the ram 48 untilthe edges of the workpiece 31 have been appreciably formed and theworkpiece pressed well into the cavity 12. As the formation continues,with the ram 48 being pressed deeper and deeper into the cavity 12, theconcavity 60 gradually disappears as the lead 48 causes the edges of theworkpiece 31 to move down around the rim section 18 and into the cavity12. By the time the center portion of the workpiece 31 is contacted bythe lead 48, through the gradual elimination of the concavity 60, theworkpiece has been well formed and considerably pressed down into thecavity 12, so that the pressure on the center of the workpiece 31 is notsufficient to cause ballooning or thinning. v 7

FIG. 11 illustrates another variant feature wherein the tiny shoulder 62at the mouth of the cavity 12 is depressedbelow the rim 13 instead ofbeing above the rim. This provides a useful means for accuratelycentering the workpiece sheet 31 over the mouth of the cavity 12.

As noted, the depression or concavity 60 of FIG. 11 is useful in theformation of very hard-to-form workpieces 31. With softer metalsaflat-faced ram 48, as shown in FIG. 9, has been found to be quitesatisfactory.

A further variant of the apparatus shown in FIGS. 9 and 11 is seen inFIG. 12, wherein the malleable ram 48 is confined by the pressure ring20 to an area which does not extend out even tothe periphery of themouth or entrance rim section 18 of the cavity 12. The portion of theworkpiece 31 which extends outside of the periphery of the ram 48 issufficiently small, and the curvature of the entrance rim section 18 isof sufficiently low radius that the lead 48 is able to flow outwardlybetween 20 and 31 and produce a downward pressure on the outer edge ofthe workpiece 31, holding it firmly against the entrance rim section 18and thus precluding undesirable folding or creasing. Once the outer edgeof the workpiece 31 has been drawn or moved inwardly, within theperiphery of the ram 48, the operation proceeds substantially as theembodiments heretofore described.

A still further variant of the apparatus is shown in FIG. 13, whereinthe outer periphery of the ram 48 extends outwardly beyond the outeredge of the workpiece 31 and the cavity 12 but still lies within theouter periphery of the rim 13. Thus, the lead is still confined so thatit cannot move the outer edges of the sheet 31 down over the shoulder15. This variant performs satisfactorily, particularly if recessedasshown at 60, but is relatively inefficient because of the necessity forflowing the outer portion of the ram 48 inwardly as the formingoperation proceeds. It is apparent that a novel feature of thisinvention as exemplified by all the apparatus and the methods set forthabove is that the workpiece is never in tension but is always maintainedin compression by a material more malleable than the workpiece.

FIG. 14 illustrates a contoured product of noncircular configurationwhich, however, like that of FIG. 6, has double curvature, i.e.,curvature in orthogonal planes, and, hence, is ideally suited toformation by the techniques of the present invention. The shape of thecavity 12 for forming the shape shown in FIG. 14 is, of

course, exactly the same as the shape of the outer sur- 6 modecontemplated, it is recognized that departures may be made therefromwithin the scope of the invention which is, therefore, not to be limitedto the details disclosed herein, but is to be afforded the full scope ofthe invention as hereinafter claimed.

What is claimed is:

1. Forming apparatus, comprising:

a die cavity having a concave terminal portion formed to theconfiguration of a desired finished workpiece, and having a curved rimportion sloping from a lateral extremity into the terminal portion, saidlateral extremity-being the peripheral form of a workpiece at thebeginning of formation;

a malleable ram having a periphery substantially conforming to saidlateral extremity of said rim portion, said ram characterized by beingextrudable under pressure into conformity with said die cavity;

means for moving said ram into said die cavity; and

means to confine said malleable ram fully within said lateral extremityof said rim portion during workpiece formation. I

2. Apparatus as defined in claim 1 further characterized in that meansis provided to confine the action of said extrudable ram to the wallarea of said cavity.

3. The apparatus as defined in claim 1, further characterized by saidram being a composite of a central core of material which isnon-malleable under pressure and temperature conditions which render theremainder of the ram extrudable to fill the die cavity, said centralcore extending axially of the ram to a forward end,

a malleable collar surrounding the core, said core confining the actionof said collar to the wall area of said cavity; and

said moving means moves said collar into said cavity.

4. The apparatus as defined in claim 3, further characterized by meansfor holding said central core against the surface of a workpiece with asnug pressure below a work draw pressure which would be sufficient tosupply significant draw forces to a workpiece.

5. An extrudable ram for deep-draw forming, comprising a compositeconstruction having a central core and a perimeter portion, said corebeing of material having substantially greater resistance to extrusiondeformation than the material of said perimeter portion.

6. The apparatus as defined in claim 4 further characterized in that thesaid central core has a flared forward end for receiving forward drivingpressure from the malleable collar.

7. The apparatus as defined in claim 4 further characterized in that apressure-sensitive means is located on the said central core forwardend;

means provided separately from said collar driving means for drivingsaid core against a workpiece; and

said pressure-sensitive means having a control effect over said meansdriving the core for holding the core against a workpiece with onlysufficient pressure to actuate said pressure-sensitive means.

8. The apparatus as defined in claim 1 further characterized by areceding platform in said die cavity, operating in a path between aworkpiece contact position at the beginning of forming action to aretracted position to the die extreme;

pressure-sensing means on said platform for sensing pressure appliedthereto by said workpiece; and means responsive to said pressure-sensingmeans to retract said platform as forming action proceeds formaintaining the support pressure of said platform at a predeterminedmaximum.

9. The apparatus as defined in claim 4 further characterized in that thecentral core has a face end formed to about a workpiece blank in thecentral area thereof spaced from said rim lateral extremity;

a pressure-sensing means in said core face end for detecting andresponding to a pressure; and

drive means independent of said means driving the collarand responsiveto said sensing means for forcing said core to follow along with areceding workpiece as it is formed by said malleable collar, said corethereby excluding the malleable material from the central area, andconfining all forming pressures to the side walls of said cavity.

10. The process of drawing a sheet into a contoured form, comprising thesteps of:

providing a die cavity having a bottom portion of a desired cavity formfor a finished workpiece, and a sloping entrance rim portion leadinginto said bottom portion;

placing a workpiece over said die cavity;

placing an extrudable ram over said workpiece substantially conformingto the perimeter of the workpiece; and

forcing said ram to first contact the extremities of said workpiece atsaid rim portion and thereafter extrude from the mass of the ram intosaid cavity along the walls of the die cavity.

11. The process as defined in claim 10 further characterized in the stepof withdrawing the extruded ram from the die cavity, and thereafterforcing the extruded ram against a surface to compress the ram back toits original form suitable for reuse in forming another workpiece.

12. The process as defined in claim 10 further characterized in the stepof confining said extrusion to an annular area adjacent the wall of thedie throughout a major portion of the formation.

13. The process as defined in claim 10 further characterized in the stepof providing said ram as a component of a core piece and collar, withsaid core piece of non-extrudable material under the pressure andtemperature conditions which render the collar extrudable;

placing said core piece in the center of said collar;

and

holding said core piece in contact with the workpiece surface withlittle effective draw pressure, and simultaneously extruding said collarto form the workpiece from the edge area.

14. A process for forming a sheet into a contoured configurationcomprising: placing the sheet over the mouth of a die cavity having aperiphery defining the cavity mouth; forcing the sheet into the cavityunder continuous compression by a substance more malleable than thesheet.

15. The process of forming a sheet into a cavity die, comprising theextrusion of a malleable ram into the die with the sheet between the ramand die, by forming the die with a flared mouth portion extending to aperipheral edge conforming to the size of a workpiece blank, and causingthe ram to first seat on the edge of the blank on the flared portion andthereafter extrude into the die with the workpiece free to ride downinto the die under the extrusion action.

16. Process for forming a sheet into a contoured configuration,comprising:

placing the sheet over the mouth of a die cavity; forcing the sheet intothe cavity by applying pressure against the sheet, initially around theperiphery of the cavity, and thence closer to the center of the cavity;at all times progressing the pressure only inwardly toward said center;thereby allowing the edges of the sheet to be drawn only inwardly; andthus flowing the sheet into a contoured configuration, without thinningor folding the sheet. 17. Process of forming a sheet into a contouredconfiguration, comprising:

positioning the sheet over the mouth of a die cavity; and forcing thesheet into the cavity by applying pressure to the sheet around theperipheral portion of the cavity, at all times permitting the edges ofthe sheet to be moved inwardly into the cavity. 18. Process inaccordance with claim 2, including additionally the step of steadilymoving said pressure inwardly toward the center of the cavity, therebymoving the edges of the sheet inwardly into the cavity without foldingor thinning of the sheet. 19. Process of forming a sheet into acontoured configuration, comprising:

placing the sheet over the mouth of a die cavity having an outwardlyflaring rim section; forcing the sheet into the cavity by applyingpressure opposite said flaring rim section, thereby to draw the edges ofthe sheet into the cavity; and progressively thereafter moving thepressure inwardly toward the center of the cavity to draw the sheet intoconformity with the cavity configuration, without thinning or foldingthe sheet, at all times permitting the edges of the sheet to be movedinto the cavity. 20. Process of forming a sheet into a contouredconfiguration, comprising:

placing the sheet over the mouth of a die cavity having a peripherydefining the cavity mouth; forcing the sheet into the cavity by applyingpressure against the sheet, initially around said periphery and thenceprogressively inward toward the center of the cavity; at all timesconfining said pressure to the area said periphery; and flowing thesheet into the contoured configuration while maintaining substantiallyconstant sheet thickness. 21. Process for forming a sheet into acontoured configuration, comprising:

placing the sheet over the mouth of a cavity formed in a die having arim surrounding said mouth; forcing the sheet into the cavity byapplying pressure against the sheet, initially around the periphery ofthe cavity and thence closer to the center of the cavity; confining saidforce at all times within said rim, thereby allowing the edges of thesheet to be moved only inwardly; and

flowing the sheet into the contoured configuration while maintainingsubstantially constant sheet thickness. 22. Apparatus for forming asheet into a contoured configuration, comprising:

within means forming a cavity having a periphery defining the cavitymouth;

malleable ram means for forcing into said cavity a sheet of materialplaced over said mouth; and

means for confining said ram means within said periphery while leavingsaid sheet of material free of restraint against lateral movementinwardly of the cavity.

23. Apparatus for forming a sheet into a contoured configuration,comprising:

a die having a cavity and a rim contiguously sur rounding said cavity,the mouth of said cavity de- Dedication 3,774,43O.Walte1- D. Greer,Lynwood, and Richard 0. Sohlicht, Seal Beach, Calif. METAL FORMING.Patent dated Nov. 27; 197 8. Dedication filed June 17 1976, by theassignee, The Gawett Uorpomtion. Hereby dedicates to the Public theentire remaining term of said patent.

[Ofiioz'al Gazette August 1'7, 1.976.]

1. Forming apparatus, comprising: a die cavity having a concave terminalportion formed to the configuration of a desired finished workpiece, andhaving a curved rim portion sloping from a lateral extremity into theterminal portion, said lateral extremity being the peripheral form of aworkpiece at the beginning of formation; a malleable ram having aperiphery substantially conforming to said lateral extremity of said rimportion, said ram characterized by being extrudable under pressure intoconformity with said die cavity; means for moving said ram into said diecavity; and means to confine said malleable ram fully within saidlateral extremity of said rim portion during workpiece formation. 2.Apparatus as defined in claim 1 further characterized in that means isprovided to confine the action of said extrudable ram to the wall areaof said cavity.
 3. The apparatus as defined in claim 1, furthercharacterized by said ram being a composite of a central core ofmaterial which is non-malleable under pressure and temperatureconditions which render the remainder of the ram extrudable to fill thedie cavity, said central core extending axially of the ram to a forwardend, a malleable collar surrounding the core, said core confining theaction of said collar to the wall area of said cavity; and said movingmeans moves said collar into said cavity.
 4. The apparatus as defined inclaim 3, further characterized by means for holding said central coreagainst the surface of a workpiece with a snug pressure below a workdraw pressure which would be sufficient to supply significant drawforces to a workpiece.
 5. An extrudable ram for deep-draw forming,comprising a composite construction having a central core and aperimeter portion, said core being of material having substantiallygreater resistance to extrusion deformation than the material of saidperimeter portion.
 6. The apparatus as defined in claim 4 furthercharacterized in that the said central core has a flared forward end forreceiving forward driving pressure from the malleable collar.
 7. Theapparatus as defined in claim 4 further characterized in that apressure-sensitive means is located on the said central core forwardend; means provided separately from said collar driving means fordriving said core against a workpiece; and said pressure-sensitive meanshaving a control effect over said means driving the core for holding thecore against a workpiece with only sufficient pressure to actuate saidpressure-sensitive means.
 8. The apparatus as defined in claim 1 furthercharacterized by a receding platform in said die cavity, operating in apath between a workpiece contact position at the beginning of formingaction to a retracted position to the die extreme; pressure-sensingmeans on said platform for sensing pressure applied thereto by saidworkpiece; and means responsive to said pressure-sensing means toretract said platform as forming action proceeds for maintaining thesupport pressure of said platform at a predetermined maximum.
 9. Theapparatus as defined in claim 4 further characterized in that thecentral core has a face end formed to about a workpiece blank in thecentral area thereof spaced from said rim lateral extremity; apressure-sensing means in said core face end for detecting andresponding to a pressure; and drive means independent of said meansdriving the collar and responsive to said sensing means for forcing saidcore to follow along with a receding workpiece as it is formed by saidmalleable collar, said core thereby excluding the malleable materialfrom the central area, and confining all forming pressures to the sidewalls of said cavity.
 10. The process of drawing a sheet into acontoured form, comprising the steps of: providing a die cavity having abottom portion of a desired cavity form for a finished workpiece, and asloping entrance rim portion leading into said bottom portion; placing aworkpiece over said die cavity; placing an extrudable ram over saidworkpiece substantially conforming to the perimeter of the workpiece;and forcing said ram to first contact the extremities of said workpieceat said rim portion and thereafter extrude from the mass of the ram intosaid cavity along the walls of the die cavity.
 11. The process asdefined in claim 10 further characterized in the step of withdrawing theextruded ram from the die cavity, and thereafter forcing the extrudedram against a surface to compress the ram back to its original formsuitable for reuse in forming another workpiece.
 12. The process asdefined in claim 10 further characterized in the step of confining saidextrusion to an annular area adjacent the wall of the die throughout amajor portion of the formation.
 13. The process as defined in claim 10further characterized in the step of providing said ram as a componentof a core piece and collar, with said core piece of non-extrudablematerial under the pressure and temperature conditions which render thecollar extrudable; placing said core piece in the center of said collar;and holding said core piece in contact with the workpiece surface withlittle effective draw pressure, and simultaneously extruding said collarto form the workpiece from the edge area.
 14. A process for forming asheet into a contoured configuration comprising: placing the sheet overthe mouth of a die cavity having a periphery defining the cavity mouth;forcing the sheet into the cavity under continuous compression by asubstance more malleable than the sheet.
 15. The process of forming asheet into a cavity die, comprising the extrusion of a malleable raminto the die with the sheet between the ram and die, by forming the diewith a flared mouth portion extending to a peripheral edge conforming tothe size of a workpiece blank, and causing the ram to first seat on theedge of the blank on the flared portion and thereafter extrude into thedie with the workpiece free to ride down into the die under theextrusion action.
 16. Process for forming a sheet into a contouredconfiguration, comprising: placing the sheet over the mouth of a diecavity; forcing the sheet into the cavity by applying pressure againstthe sheet, initially around the periphery of the cavity, and thencecloser to the center of the cavity; at all times progressing thepressure only inwardly toward said center; thereby allowing the edges ofthe sheet to be drawn only inwardly; and thus flowing the sheet into acontoured configuration, without thinning or folding the sheet. 17.Process of forming a sheet into a contoured configuration, comprising:positioning the sheet over the mouth of a die cavity; and forcing thesheet into the cavity by applying pressure to the sheet around theperipheral portion of the cavity, at all times permitting the edges ofthe sheet to be moved inwardly into the cavity.
 18. Process inaccordance with claim 2, including additionally the step of steadilymoving said pressure inwardly toward the center of the cavity, therebymoving the edges of the sheet inwardly into the cavity without foldingor thinning of the sheet.
 19. Process of forming a sheet into acontoured configuration, comprising: placing the sheet over the mouth ofa die cavity having an outwardly flaring rim section; forcing the sheetinto the cavity by applying pressure opposite said flaring rim section,thereby to draw the edges of the sheet into the cavity; andprogressively thereafter moving the pressure inwardly toward the centerof the cavity to draw the sheet into conformity with the cavityconfiguration, without thinning oR folding the sheet, at all timespermitting the edges of the sheet to be moved into the cavity. 20.Process of forming a sheet into a contoured configuration, comprising:placing the sheet over the mouth of a die cavity having a peripherydefining the cavity mouth; forcing the sheet into the cavity by applyingpressure against the sheet, initially around said periphery and thenceprogressively inward toward the center of the cavity; at all timesconfining said pressure to the area within said periphery; and flowingthe sheet into the contoured configuration while maintainingsubstantially constant sheet thickness.
 21. Process for forming a sheetinto a contoured configuration, comprising: placing the sheet over themouth of a cavity formed in a die having a rim surrounding said mouth;forcing the sheet into the cavity by applying pressure against thesheet, initially around the periphery of the cavity and thence closer tothe center of the cavity; confining said force at all times within saidrim, thereby allowing the edges of the sheet to be moved only inwardly;and flowing the sheet into the contoured configuration while maintainingsubstantially constant sheet thickness.
 22. Apparatus for forming asheet into a contoured configuration, comprising: means forming a cavityhaving a periphery defining the cavity mouth; malleable ram means forforcing into said cavity a sheet of material placed over said mouth; andmeans for confining said ram means within said periphery while leavingsaid sheet of material free of restraint against lateral movementinwardly of the cavity.
 23. Apparatus for forming a sheet into acontoured configuration, comprising: a die having a cavity and a rimcontiguously surrounding said cavity, the mouth of said cavity definingthe inner periphery of said rim, the outer periphery of said rim beingspaced outwardly of said mouth and substantially co-planar with saidinner periphery; malleable ram means for forcing into said cavity asheet of material placed over said cavity mouth; and means for confiningsaid ram means within the outer periphery of said rim while leaving saidsheet of material unrestrained against lateral movement inwardly of thedie cavity.